A capable and professional commander, Toreth once received the Sotarek Citation for winning a decisive victory over the Klingons, despite half her squadron being destroyed in an ambush due to faulty intelligence. The intelligence officer responsible for the mission was subsequently executed.
Toreth's father had been murdered by the Tal Shiar for speaking out against the government. As a result, Toreth despised the Tal Shiar and viewed their supposed "protection" of the Empire with contempt.
In 2369, Toreth was ordered to deliver some unidentified cargo, accompanied by Tal Shiar operative Major Rakal, to the Kaleb sector for transfer to a Corvallen freighter. The cargo actually contained Vice-Proconsul M'ret and his aides in stasis, who were defecting to the Federation. The operation was arranged by Spock, and Deanna Troi was surgically altered to take Rakal's place. Toreth made no secret of her opinion of the Tal Shiar, and tensions between her and Troi escalated after Subcommander N'Vek, a member of the underground, destroyed the freighter claiming he was acting under Rakal's orders. Troi had just before determined the Corvallen captain to be untrustworthy.
Though outraged by Rakal's undermining of her authority, Toreth nevertheless obeyed Rakal's orders to take the Khazara into Federation space to deliver the cargo themselves. However, before they departed the USS Enterprise-D arrived at the scene. Seeing an opportunity, Troi told N'Vek to sabotage the cloaking device so the Enterprise-D could detect them. Toreth, suspecting that their cloak had been compromised, set the Khazara on a collision course with the Enterprise-D, reasoning that if their position had indeed been revealed the Federation starship would move to avoid them. When the Enterprise-D backed off, Toreth planned to decloak and open fire.
To avert the attack on the Enterprise-D, Troi seized command of the bridge with the authority of the Tal Shiar and claimed that she would trick the Enterprise-D into lowering their shields through negotiation. When the Enterprise-D did so, N'Vek transported their living cargo to the other ship through a low-power disruptor beam. Discovering the ruse, Toreth regained control of the bridge and had N'Vek killed when he tried to intervene. Toreth ordered the Khazara to return to Romulan space, though the Enterprise-D was able to retrieve Troi. (TNG: "Face of the Enemy")